Products to measure the quality and/or quantity of fuels (liquids or gases) with optional control features to further optimize the energy efficiency of a machine (using energy: users), fuel manufacturers (producing energy or mixing such as biofuels: producers), manufacturers of other products (general manufacturers), mixing, and/or monitoring the authenticity of fuel (fuel custody transfer and quality control), detection of fuel adulteration, as well as other applications. The fluid quality and/or quantity monitoring may be accomplished by sensors with or without actuators to measure and optionally control one or more parameters, including without limitation volumetric flow, mass flow, density, concentration, viscosity, dielectric constant, refractive index, pH, color, dissolved oxygen, level, energy content, heat capacity, content, composition, BRIX, API, temperature, and other specific quality indicators. The measured parameters may be used to monitor with optional control the quality and/or quantity of the fluids, devices that use the fluids, or fluid consumers. These products can be used in a variety of applications and fields